1. Field of the Invention
The present invention relates to new intermediates for the preparation of (meth)acrylated photoinitiators and to a method for the preparation of (meth)acrylated photoinitiators.
2. Description of the Related Art
A free radical photoinitiator is a chemical compound that initiates a polymerization of monomers when exposed to actinic radiation by the formation of a free radical. Photoinitiators are frequently used in UV-curable compositions, such UV curable inkjet inks.
For coating or printing on food packaging materials, it can be necessary to use a copolymerizable photoinitiator due to the possible or known toxicity of a photoinitiator and its degradation products.
U.S. Pat. No. 4,922,004 (MERCK) discloses acryloyloxyphenyl hydroxypropyl ketones and other types of copolymerizable photoinitiators. These photoinitiators are prepared using (meth)acryloyl chloride.
It is commonly known that (meth)acryloyl chloride is highly reactive and limited in stability. It is often contaminated with cyclic dimers requiring destillation prior to use. Combined with the highly toxic nature of (meth)acryloyl chloride, the limited availability on the market and the high cost, synthetic methods using (meth)acryloyl chloride are not well suited for the preparation of (meth)acrylated photoinitiators on an industrial scale.
Acrylates and methacrylates in general can be prepared, using different synthetic strategies. Classically, acid catalyzed esterification of acrylic or methacrylic acid with the required alcohol is used. However, this method is incompatible with acid sensitive functional groups as e.g. in several α-hydroxy-ketone photoinitiators, requiring a different synthetic strategy.
It is highly desirable to be able to obtain (meth)acrylated photoinitiators with high purity, according to a simplified process compared to state of the art processes, avoiding the highly reactive, unstable and toxic (meth)acryloyl chloride.